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Liar's brain always speaks the truth

Brain scans show that the brains of people who are lying look very different from those of people who are telling the truth, US researchers have said.

29 Nov 2004 21:14 GMT

Lying causes activity in the frontal part of the brain

The study, using functional magnetic resonance imaging or fMRI, not only sheds light on what goes on when people lie but may also provide new technology for lie-detecting, the researchers said on Monday.

"There may be unique areas in the brain involved in deception that can be measured with fMRI," said Dr Scott Faro, director of the Functional Brain Imaging Centre at Temple UniversitySchool of Medicine in Philadelphia.

"There may be unique areas in the brain involved in truth-telling," Faro added at a news conference.

Faro and colleagues tested 10 volunteers. Six of them were asked to shoot a toy gun and then lie and say they did not do it. Three others who watched told the truth about what happened. One volunteer dropped out of the study.

Volunteers

There were seven areas of activation in the liar's brain

While giving their testimony, the volunteers were hooked up both to a conventional polygraph and also had their brain activity imaged using fMRI, which used a strong magnet to provide a real-time picture of brain activity.

There were clear differences between the liars and the truth-tellers, Faro's team told a meeting in Chicago of the Radiological Society of North America.

"We found a total of seven areas of activation in the deception [group]," he said. "We found four areas of activity in the truth-telling arm."

More effort lying

Overall, it seemed to take more brain effort to tell a lie than to tell the truth, Faro found.

Lying caused activity in the frontal part of the brain - the medial inferior and pre-central areas, as well as the hippocampus and middle temporal regions and the limbic areas.

Some of these are involved in emotional responses, Faro said.

"There may be unique areas in the brain involved in truth-telling" Dr Scott Faro, Temple University School of Medicine, Philadelphia

During a truthful response, the fMRI showed activation of parts of the brain's frontal lobe, temporal lobe and cingulate gyrus.

Faro said the study was small and limited. Volunteers were not asked to try especially hard to deceive the equipment, he said - noting that it has been documented that some people can fool a polygraph using various techniques.

Using fMRI as a lie detector is expensive, but it may be worthwhile in some cases - such as trying to question a terrorism suspect, or in a high-profile corporate crime case, Faro said.